Education

Orca Whale Facts

Orcinus orca, better known as killer whales, are toothed cetaceans (odontocetes) and are the largest member of the dolphin family (Delphinidae). They are found in all of the world's oceans and are the most widespread mammal after the human being. Orcas are mainly black with white markings on their bellies, behind their dorsal fins and on the sides of their heads. There are three known races of orca: residents, transients and offshores. Resident orcas travel in large family groups, or pods, are very vocal and their diet consists of fish and squid. Transient orcas travel solitarily or in small groups, vocalize infrequently and eat marine mammals, including seals, porpoises and small whales. Offshore orcas travel in very large groups, use frequent vocalizations and are thought to eat schooling fish. Many details about offshore orcas are still unknown, as they were only discovered in the early 90's.

Killer whales are sexually dimorphic, meaning that the males are larger than the females. Male orcas reach a maximum length of 9 meters (m) and a maximum weight of 10,000 kilograms (kg). Females reach a maximum length of 7 m and a maximum weight of 7500 kg. Another size difference between male and female orcas is seen in the dorsal fin, the fin on the back of the orca. Adult males sport a dorsal fin that can reach a maximum height of 2m. Females and juvenile male orcas have dorsal fins that reach 1 m in height. Juvenile male orcas go through a pubescent period between approximately 12 and 17 years of age that involves a "sprouting" of their dorsal fin. During this time the fin grows from 1 m to 2 m in height and is very unstable giving it a wobbly appearance. The fin gains stability over time and is upright and rigid in adult male orcas.

Killer whales travel in groups called pods. The number of individuals in a pod varies with race of orca. Resident orcas travel in large pods, averaging 20 or more whales per pod. Each pod is made up of a family of killer whales and is headed by the eldest female, or matriarch. Once a killer whale is born into a pod it remains with that pod for its entire lifespan. Male orcas typically live for 45-50 years and female orcas for 75-80 years. Female orcas begin to reproduce at 12-14 years of age. They have a calf every 3-5 years up until the age of approximately 45 at which they go through a menopause period. There is a 13-16 month gestation period after which the female gives birth to typically one calf at a time. The calves are approximately 2.5 m long and weigh around 200 kg. The calves nurse for the first year of their life. The mother orca secretes very thick milk from mammary slits that are located on her belly. The milk is very nutritious, with a 50% fat content. The calves remain very close to their mothers for the first seven years of their lives after which they begin to gain some independence, although they remain with their mothers for their entire life. The calves learn everything they know from their mothers and family members, from the minute they are born and their mothers push them to the surface to take their first breath through the blowhole on the top of their head. Orcas in a pod have a very strong social structure that is best displayed during periods of rest. When orcas rest, they shut down one hemisphere of their brain at a time. The entire pod congregates into a resting line and moves together in a series of synchronized dives. The resting can carry on for hours, with the whales remaining side-by-side for this entire time.

Orcas make a variety of sounds, ranging from clicks to whistles to chirps. The vocalizations of orcas are pod-specific, allowing for identification of individual pods by their characteristic vocalizations. Each pod has a slightly different dialect, with the similarity between dialects indicating relatedness between pods. It is thought that orcas mate with other orcas that have the least similar dialect to their own, assuring that they are not mating with a relative. This decreases the chance of inbreeding and maximizes genetic diversity. Orcas also use another form of sound to sense their surroundings. Orcas echolocate, which is when they produce a series of clicks that echo off of objects in front of them. They receive the echoed clicks and their brains process the clicks into an image. The image is received as an x-ray, allowing the orcas to "see" the internal structure of the object that the clicks echo off of. The click trains can vary in frequency and can be intensified into a beam strong enough to temporarily stun fish. The orcas receive sound through their lower jaw, which is filled with a fat-like fluid and is attached to the inner ear structure.

Orcas display many types of physical behaviour. Breaching is when the orca launches its entire body out of the water and lands on its side. The reasons why orcas breach are not fully understood, but it is thought to be a playful behaviour, which could also be used for communication and to knock off an ecto-parasites that may have settled onto the orcas skin. Spyhopping is when an orca brings the front half of its body out of the water. This behaviour allows the orcas to get a good look at the surrounding area above the water. Orcas have good eyesight above and below the water and are believed to use landmarks to identify familiar territory. Orcas also display other showy behaviours such a cartwheels, tail-lobs and fin slaps. These behaviours are used for communication as well as amusement by the orcas. Orcas have very sensitive skin and are often seen rolling on top of one another. Orcas will swim through forests of bull kelp and drape the kelp over their tail flukes and dorsal fin and drag the kelp between their teeth.

The population of orcas that reside in the waters surrounding southern Vancouver Island is made up of three pods; the J, K and L pods. These pods, known as the Southern Residents, frequent the waters making up the Salish Sea area in the summer months, feasting on salmon populations that are running from the Pacific Ocean to the Fraser River to spawn. The Southern Residents have been researched for the last 35 years and each orca has been photo-identified. Each orca has a marking on their back, behind the dorsal fin. This patch, called the saddle patch, is different on each whale and can be used to identify the orcas. This allows for the approximately 90 orcas that make up the Southern Residents to be identified. The three Southern Resident pods mate among each other and do not interbreed with the Northern Residents, the population of orcas that inhabit the waters on the northern end of Vancouver Island. The Southern Residents are currently listed as endangered by both Canada and the United States.